It is often necessary to remove various forms of flowable material from a well. The flowable material is essentially non-gaseous and may include a significant liquid or sludge component. Particulate solids may be included in the flowable material to various degrees.
One example of the need to remove flowable material of this type occurs in landfill gas wells. Landfills typically contain an essentially liquid component or leachate which seeps into the well, and this progressively diminishes the recovery of landfill gas from the well.
To remove this flowable material, a gas-operated pump can be provided in the well. A gas-operated pump of this type may include, for example, a housing, at least one aperture in the housing leading to an interior chamber within the housing and a pressure-responsive valve for opening and closing the aperture. The valve is normally open so that the flowable material from the well can enter the chamber. Gas under pressure is then provided through a conduit to the pump to close the valve to terminate entry of the flowable material into the chamber. In addition, the gas under pressure within the chamber forces the flowable material from the chamber out of the pump. A pump of this type is shown, for example, in Elliott U.S. Pat. No. 2,412,723.
It is known to use liquid level detectors to control the supply of gas under pressure to the pump. Liquid level detectors are typically electrically operated, and this may require the running of thousands of feet of electrical wiring from a central control station to numerous remotely located wells. In addition, electrical components and conductors are undesirable in hazardous environments, such as gas wells.